Artificial daylight lamp



Nov. 29, 1955 D. s. AMOUR 2,725,461

ARTIFICIAL DAYLIGHT LAMP Filed Nov. 12, 1952 United States Patent O ARTIFICIAL DAYLIGHT LAMP David S. Amour, Long Beach, Calif., assigner, by mesne assignments, to Analite Corporation, Fresno, Calif., a corporation of California f Application November 12, 1952, Serial No. 319,867

8 Claims. (Cl. 24d-1.1)

This invention relates to an artificial daylight lamp whereby natural daylight can be closely approximated. The definition of natural daylight consists of and is represented by a completely overcast sky, or by a total mixture of sunlight and skylight, regardless of the amount of overcast, and also represents the suns radiation outside of the earths atmosphere. The color temperature of natural daylight, also termed Abbots daylight, is approximately 6500" Kelvin, but it may vary from 6000" to 7500 K.

An object of my invention is to provide an artificial lamp which will very closely approximate the ideal natural daylight curve so that color classing can be effectivelyaccomplished, and objects will show a true rendition of color.

A feature of my invention is to produce an artificial lamp, the spectral curve of which approximates natural daylight and this lamp utilizing both fiuorescent and incandescent lamps.

Another feature of my invention is to provide a novel artificial lamp of the character stated which includes a diffuser plate through which all of the light passes from the various artificial light sources, this diffuser plate having the property of effectively diffusing the light whichl passes therethrough. The diffuser plate further so mixes the various colors of light from theindividual light sources so that the eye does not see any of the individual colors, but only the final mixture.

A further feature of my invention is to provide a novel artificial daylight lamp in which there is a low brightness but a large area source which materially adds to eye comfort, and is also desirable when viewing many objects.

A further object of my invention is to provide an arti- I ficial lamp construction in which a plurality of different colored lamps are provided within the lamp inclosure and this lamp inclosure having a diffuser plate at the bottom,

with the various colored lamps being so positioned and arranged within the lamp inclosure that each group of colored lamps will uniformly illuminate the diffuser plate when lighted alone.

Other objects, advantages and features of invention may appear from the accompanying drawing, the subjoined detailed description and the appended claims.

In the drawings- Figure l is a perspective view of a lamp embodying the principles of the subject invention.

Figure 2 is a diagrammatic transverse sectional View of the lamp shown in Figure 1.

Figure 3 is a spectral response curve in which the artificial daylight curve is light.

Referring more particularly to the drawing, the numeral 1 indicates a housing which is substantially rectangular and formed of a suitable opaque substance. This housing may be metal, if desired. The inside surface 2 of the housing 1 is very highly reflective, that is, it can be enamel coated or otherwisetreated to produce a highly reflective surface. The bottom of the housing 1 is closed by the plotted with ideal natural dayabsorption range of the filter.

Pce

diffuser plate 3. This diffuser plate may be made of glass, plastic, fabric and many other materials. Translucent white plastic is one of the best materials for this purpose, since it has high transmission and low absorption losses.

The diffuser plate 3 performs two functions. First, it is preferable that no color in the lighting unit can be seen by the eye, except the final mixture. The diffuser plate performs this function. Secondly, the diffuser plate provides a low brightness and a large area source, which is essential for eye comfort, and also is desirable when viewing many objects, especially highly specular or shiny objects.

In the embodiment of my invention, shown in Figures l and 2, four types of lamps are used. In placing these lamps two conditions must be satisfied. First, that all lamps shall have substantially good access to the exit aperture, which is the diffuser plate 3, and, second, that each lamp when lighted by itself provides uniform illumination of the diffuser plate 3. These lamps are preferably all cylindrical in form but other forms may also be used and the lowest bank of lamps indicated at 4 consists of three daylight lamps, these lamps being fluorescent. They extend parallel to the diffuser plate 3 and from end to end of the housing 1 and are positioned in the usual terminals provided for tubular lamps. The daylight lamps have a color temperature of approximately 6500 K. Arranged above the group of three daylight lamps 4, I provide a group of two blue lamps 5, these lamps being also fluorescent and tubular in shape as are the lamps 4. The

two lamps 5 are positioned above the horizontal center line of the lamps l and are preferably arranged in the spaces between the center and the outside lamps 4. These blue iiuorescent lamps have a color temperature theoretically computable as approximately 30,000" K. A pair of incandescent lamps 6, having a color-temperature of approximately 2800 K., are arranged above the plane of the blue fluorescent lamps 5 and also are positioned adjacent to the side walls of the housing 1, and rather close to the top of the housing. In the approximate center of the housing 1 and close to the top thereof, I provide a single green fluorescent lamp 7, also tubular in form, and positioned between the two incandescent lamps 6. The corresponding color temperature of the green lamp is not even theoretically computable with sufiicient accuracy to be reliable or meaningful for definition purposes. Its chromatic characteristics can be defined, however, as providing a markedly peaked curve at 5,250 Angstrom units when relative energy is plotted against wave lengths. The incandescent lamps 6 are added to till out the red end of the spectrum toward 700 millimicrons. With the blue and daylight type iiuorescent lamps a region near 540 vmillimicrons is deficient, since this is in the green region.

The deficiency is satisfied by fluorescent tube 7.

In Figure 3 l have shown the spectral response curve in which the curve 8 is ideal natural daylight and the curve 9 is the spectral response of the artificial daylight lamp shown in Figures l and 2. It will be noted that the artificial curve closely approximates the natural daylight curve. Since the fluorescent lamp is basically a mercury discharge lamp, a certain amount of visible light passes through the fluorescent coating, forming spikes of light indicatedl at l0. There are usually four of these lines or spikes of light which are quite narrow, and are very intense. Ordinary filters will not remove these lines, except by also removing all of the light within the The concentrated light lines 10, therefore, make it impossible to exactly match the daylight curve. However, a close approximation of ideal natural daylight is obtained by the lamp, as shown in Figure 3.

the addition of the green `of the incandescent lamps being i lamp which very open bottom of the housing -to the side walls -thereof and lying When all of the lamps 4, 5, 6 and 7 are lighted, the light is effectively mixed within the housing 1, 'and before the light passes the diffuser plate 3. This is the reason that the inside of the housing l preferably has a highly reflective surface. Also there are no light spots showing 'on the diffuser plate, that is, none ofthe individual lamps show any bright spots .on Vthe diffuser plate.

'In order that there be an optimum mixing of the light before it passes the diffuser plate 3, it is also required that each of the lamp clusters 4,'5, 6 and '7 'must each uniformly illuminate the diffuser plate 3 when they are lighted alone. Thus, the daylight lamps 4, the blue lamps "i5, and the green light 7, and the incandescent lights 6 .each alone uniformly illuminate the entire diffuser plate 3, and no bright spots willshow on the diffuser plate, and, therefore, the entire area of the diffuser plateis radiating daylight. In the lamps herein disclosed it will be evident that the artificial daylight curve closely approximates the ideal 'natural daylight curve and, therefore, a more effective artificial daylight lamp is provided.

Having described my invention, I claim:

1l. An artificial daylight lamp comprisingy a housing having a reflective inner opening oppositely disposed from the wall; a plurality of daylight type fluorescent lamps mounted in the housing .adjacent to the opening therein; a pair of incandescent lamps mounted in the housing adjacent to the upper wall thereof; a plurality of blue type fluorescent lamps mounted in the housing intermediate the daylight type fluorescent lamps and the incandescent lamps; and a green type fluorescent lamp mounted in the housing adjacent .to the upper wall and being positioned intermedi- 'ate and above the incandescent lamps.

2. .An artificial daylight lamp comprising an elongated housing having a highly reflective inner surface, a pair of opposite upper corners and open bottom', a diffuser plate mounted over the open bottom; a plurality of daylight type fluorescent lamps mounted in the housing in a common plane parallel to the diffuser plate and being transversely spaced from each other; a pair of incandescent lamps mounted in the housing arranged in a common plane parallel to the diffuser plate and lying substantially above the daylight type fluorescent lamps, one located in eachof the opposite upper corners of the housing; a plurality of blue type fluorescent lamps mounted in the housing in a common plane. parallel to the diffuser .plate and being located intermediate the planes containing the daylight type fluorescent lamps and the incandescent lamps, the blue typefluorcscent lamps being positioned substantially closer 'to the daylight type fluorescent lamps than to the incandescent lamps; and a green type of fluorescent lamp being mounted in equidistantly spaced relation between the .incandescent lamps and lying above .the common plane in which the incandescent lamps are located whereby the 'direct and reflected light from all of the lamps is completely and uniformly mixed to provide a combined spectral responsive characteristic for the artificial -daylight closely simulates `that of daylight.

.3. A lamp for closely simulating daylight comprisv'ing an elongated housing being substantially rectangular lin cross section and having an upper Wall, a pair of side walls depending from the upper wall and an operi bottom opposite said upper wall, the housing having a pair of upper corners defined by the intersection of each side wall with the upper wall, and the housing hav-ing an inside surface substantially completely coated with a highly reflective material; a diffuser plate enclosing the and disposed parallel to the upper Wall; three elongated tubular daylight type .fluorescent lamps mounted in the housing extending longitudinally--substantially the full length-of the housingparallel inta transversely equally spaced relation in a common plane parallel-to the diffuser plate, said common plane containing the daylight lamps lyingbelow an imaginary central plane which is parallel and equidistant from the upper wall and the diffuser plate, said daylight lamps being spaced from the diffuser plate a substantially greater distance than from the imaginary central plane; a pair of elongated tubular blue type fluorescent lamps mounted in the housing extending longitudinally substantially the full length of the housing parallel to the side walls thereof and lying in transversely spaced relation in a common plane parallel to the upper wall, the common 'plane containing the blue type lamps lying above said imaginary central plane and being spaced a substantially greater distance from the upper wall than from the imaginary central plane, said blue type fluorescent lamps being transversely positioned between the side walls of the housing in staggered relation to the daylight type fluorescent lamps whereby each of the blue type fluorescent lamps is positioned above andbetween a pair of daylight type fluorescent lamps; la pair of elongated tubular incandescent lamps mounted in the housing extending'substantially the full length of the-housing parallel to the side walls thereof and each being disposed in an upper corner of the housing, the incandescent lamps lying in a common plane parallel to the upper wall; and an elongated tubular green type fluorescent lamp mounted in the housing extending substantially the full length of the housing parallel to the side walls thereof, thegreen type fluorescent lamp being positioned intermediate the side walls and being spaced equidistantly therefrom throughout the entire length thereof, the green type fluorescent lamp being further positioned substantially closer to the upper Wall than to .said imaginary central plane and lying above thecommon .plane containing the incandescent type lamps, whereby thepositioning of the lamps in the housing in cooperation with the reflective character of the housing enables lthe light emanating from said lamp to be completely mixed before passing through the diffuser plate and whereby such complete mixing .of the lightfrom the lamps produces an artificial light closely simulating daylight.

4. An artificial daylight lamp comprising a housing having a reflective wall and a light emitting wall; a daylight type .fluorescentlight source mounted in the housing between the reflective wall and the light emitting wall in spaced relation to the emitting wall; an incandescent light source mounted in the housing between the reflective wall and the emitting wall in spaced relation to the emitting Wal-l; a fluorescent source of blue light in the housing in more greatly spaced relation to the light emitting wall than the daylight type lightsource; and a fluorescent source of green light in the housing in more greatly spaced relation to the light emitting wall than the incandescent light source.

5. Anartiflcia'i daylight lamp comprising a housing `having a reflective wall and a light emitting wall oppositely disposed from the reflective wall; a plurality of daylight type fluorescent lamps mounted in the housing in spaced relation to the reflective wall; a plurality of incandescent lamps mounted in the housing between the reflective wall und the emitting Wall;l a plurality of blue type fluorescent lamps mounted in the housing opposite to the daylight type lamps from the lightemitting wall;-and ailuorescent source of green light in thehousing opposite to itlie incandescent lamps from the light emitting wall.

6. An artificial daylight 'lamp comprising a housing having .a light emitting wall; a daylight type fluorescent lamp mounted inthe housing in spaced relation to the .light emitting wall; an incandescent lamp mounted in the housing in spaced relation to thedaylight type fluorescent lamp; `a blue type fluorescent. lamp mounted in .the nous- .ing..intermediate .the daylight type Vfluorescent lamp and the .incandescent I.larnp .and in further ,spaced .relation from the daylight .type .fluorescent lamp;

lamp, the 4daylight `type nur..

fluorescent lamp, and the blue type fluorescent lamp from the light emitting wall.

7. An artificial daylight lamp comprising a housing having a reflective inner surface and an opening oppositely disposed from the reliective surface; a diffuser plate mounted in the opening; a plurality of daylight type liuorescent lamps mounted in the housing in a common plane parallel to the diffuser plate and being transversely spaced from each other; an incandescent lamp mounted .in the housing in spaced relation to the diffuser plate and intermediate the daylight type fluorescent lamps and the reflective inner surface of the housing; a plurality of blue type fluorescent lamps mounted in the housing in a common plane parallel to the diffuser plate opposite to the plane of the daylight type uorescent lamps from the diffuser plate, said blue type lampsbeing positioned in a plane intermediate the incandescent lamp and the daylight type lamps; and a green fluorescent light source in wardly of the incandescent lamp from the diffuser' plate whereby the direct and reflected light from all of the lamps is substantially uniformly mixed to provide a combined spectral responsive characteristic for the artificial daylight lamp which very closely simulates that of daylight.

8. A lamp for closely simulating daylight comprising an elongated housing having a reflective wall, a pair of side walls extended from the reflective wall, and an opening opposite to said reflective wall; a diffuser plate closing the opening of the housing and disposed substantially parallel to the reflective wall; elongated tubular daylight type fiuorescent lamps mounted in the housing extending longi tudinally substantially the full length of the housing parallel to the side walls thereof and lying in a transversely equally spaced relation in a common plane parallel to the diffuser plate; elongated tubular blue type uorescent lamps mounted in the housing extending longitudinally substantially the full length of the housing parallel to the side walls thereof and lying in transversely spaced relation in a common plane parallel to the reflective wall between the plane of the daylight lamps and the reflective wall, said blue type fluorescent lamps being transversely positioned between the side walls of the housing in staggered relation to the daylight type fluorescent lamps whereby the blue type fluorescent lamps are positioned inwardly and between the daylight type fluorescent lamps; incandescent lamps mounted in the housing in spaced relation to the reflection wall thereof with the blue type llucrescent lamps positioned between the incandescent lamps and the daylight type fluorescent lamps; and a fluorescent source of green light in the housing inwardly of the diffuser plate, the incandescent lamps and the planes of the blue type and the daylight type fluorescent lamps whereby the positioning of the lamps in the housing in cooperation with the reflective character of the housing enables the light emanating from said lamp to be completely mixed before passing through the diffuser plate and whereby such complete mixing of the light from the lamps produces an artificial light closely simulating daylight.

References Cited in the file of this patent UNITED STATES PATENTS 

